默认情况下，FreeBSD是不支持root用户的SSH远程访问的，如果你一定要这么连接，你将会遇到如下所示的样子的错误告警：

或者这样的错误：

[root@redis python]# ssh 192.168.92.171
Password for root@freebsd:
Password for root@freebsd:
Password for root@freebsd:
Permission denied (publickey,keyboard-interactive).
[root@redis python]#

如果遇到了这样的问题，你需要对FreeBSD的SSHD做出配置上的修改：
修改后，我的配置文件【/etc/ssh/sshd_config】的状态是这样的：

root@freebsd:~ # cat /etc/ssh/sshd_config 
#       $OpenBSD: sshd_config,v 1.98 2016/02/17 05:29:04 djm Exp $
#       $FreeBSD: releng/11.0/crypto/openssh/sshd_config 296633 2016-03-11 00:15:29Z des $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

# Note that some of FreeBSD's defaults differ from OpenBSD's, and
# FreeBSD has a few additional options.

#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

# The default requires explicit activation of protocol 1
#Protocol 2

# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key

# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 1024

# Ciphers and keying
#RekeyLimit default none

# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin no
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#RSAAuthentication yes
#PubkeyAuthentication yes

# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
#AuthorizedKeysFile .ssh/authorized_keys .ssh/authorized_keys2

#AuthorizedPrincipalsFile none

#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# Change to yes to enable built-in password authentication.
#PasswordAuthentication no
#PermitEmptyPasswords no

# Change to no to disable PAM authentication
#ChallengeResponseAuthentication yes

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

# Set this to 'no' to disable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
#UsePAM yes

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
#X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation sandbox
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum FreeBSD-20160310

# no default banner path
#Banner none

# override default of no subsystems
Subsystem       sftp    /usr/libexec/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#       X11Forwarding no
#       AllowTcpForwarding no
#       PermitTTY no
#       ForceCommand cvs server

# adamhuan changed
PasswordAuthentication yes
PermitRootLogin yes
root@freebsd:~ #

而其中关键的位置，在这里：

root@freebsd:~ # cat /etc/ssh/sshd_config | grep --color -E "PermitRootLogin|PasswordAuthentication|PermitEmptyPasswords"
#PermitRootLogin no
#PasswordAuthentication no
#PermitEmptyPasswords no
# PasswordAuthentication.  Depending on your PAM configuration,
# the setting of "PermitRootLogin without-password".
# PAM authentication, then enable this but set PasswordAuthentication
PasswordAuthentication yes
PermitRootLogin yes
root@freebsd:~ #

具体意思：
PermitRootLogin，是否允许root登录
PermitEmptyPassword，是否允许空密码登录
PasswordAuthentication，是否使用口令验证

————————
另外，FreeBSD中的SSH服务可能也不是默认打开的，你可以按照下面的方式去启用。

查看服务是否运行：

root@freebsd:~ # service sshd status
sshd is running as pid 785.
root@freebsd:~ #

查看端口的监听状态：

root@freebsd:~ # netstat -an | grep --color 22
tcp4       0      0 192.168.92.171.22      192.168.92.1.4765      ESTABLISHED
tcp4       0      0 *.22                   *.*                    LISTEN
tcp6       0      0 *.22                   *.*                    LISTEN
root@freebsd:~ #

查看是否激活了SSH服务：

root@freebsd:~ # cat /etc/rc.conf
hostname="freebsd"
ifconfig_em0="DHCP"
ifconfig_em0_ipv6="inet6 accept_rtadv"
sshd_enable="YES"
# Set dumpdev to "AUTO" to enable crash dumps, "NO" to disable
dumpdev="AUTO"
root@freebsd:~ # 
root@freebsd:~ # cat /etc/rc.conf | grep --color ssh
sshd_enable="YES"
root@freebsd:~ #

除了上面这些，还有一个地方记录了与SSH有关的信息：

root@freebsd:~ # cat /etc/inetd.conf | grep --color ssh
#ssh    stream  tcp     nowait  root    /usr/sbin/sshd          sshd -i -4
#ssh    stream  tcp6    nowait  root    /usr/sbin/sshd          sshd -i -6
root@freebsd:~ #

——————————
这样，完成了上述配置之后，用root用户ssh登录FreeBSD就应该没有问题了：

[root@redis python]# ssh 192.168.92.171
Password for root@freebsd:
Last login: Fri May 26 16:55:45 2017 from 192.168.92.1
FreeBSD 11.0-RELEASE-p1 (GENERIC) #0 r306420: Thu Sep 29 01:43:23 UTC 2016

Welcome to FreeBSD!

Release Notes, Errata: https://www.FreeBSD.org/releases/
Security Advisories:   https://www.FreeBSD.org/security/
FreeBSD Handbook:      https://www.FreeBSD.org/handbook/
FreeBSD FAQ:           https://www.FreeBSD.org/faq/
Questions List: https://lists.FreeBSD.org/mailman/listinfo/freebsd-questions/
FreeBSD Forums:        https://forums.FreeBSD.org/

Documents installed with the system are in the /usr/local/share/doc/freebsd/
directory, or can be installed later with:  pkg install en-freebsd-doc
For other languages, replace "en" with a language code like de or fr.

Show the version of FreeBSD installed:  freebsd-version ; uname -a
Please include that output and any error messages when posting questions.
Introduction to manual pages:  man man
FreeBSD directory layout:      man hier

Edit /etc/motd to change this login announcement.
root@freebsd:~ # 
root@freebsd:~ # exit
logout
Connection to 192.168.92.171 closed.
[root@redis python]#

——————————————————
Done。